Dominic Ford, Editor
From the Inner Planets feed
Venus will be well placed for observation in the evening sky, shining brightly at mag -4.3.
From Ashburn, it will be difficult to observe as it will appear no higher than 16° above the horizon. It will become visible at around 20:20 (EST) as the dusk sky fades, 16° above your western horizon. It will then sink towards the horizon, setting 1 hour and 48 minutes after the Sun at 21:49.
Venus's orbit lies closer to the Sun than the Earth's, meaning that it always appears close to the Sun and is very difficult to observe most of the time.
It is observable only for a few weeks each time it reaches greatest separation from the Sun – moments referred to as greatest elongation.
On these occasions, however, Venus is so bright and conspicuous that it becomes the third brightest object in the sky after the Sun and Moon. It is often called the morning or evening star.
Venus's phase varies depending on its position relative to the Earth. When it passes between the Earth and Sun, for example, the side that is turned towards the Earth is entirely unilluminated, like a new moon.
Conversely, when it lies opposite to the Earth in its orbit, passing almost behind the Sun, it appears fully illuminated, like a full moon. However, at this time it is also at its most distant from the Earth, so it is actually fainter than at other times.
Venus shows an intermediate half phase – called dichotomy – at roughly the same moment that it appears furthest from the Sun, at greatest elongation. The exact times of the two events may differ by a few hours, only because Venus's orbit is not quite perfectly aligned with the ecliptic.
Venus in coming weeks
The key moments in this apparition of Venus are as follows:
|15 Aug 2018 01:09 EDT||– Venus at dichotomy|
|17 Aug 2018 03:58 EDT||– Venus at greatest elongation east|
|25 Sep 2018 00:17 EDT||– Venus at greatest brightness|
|26 Oct 2018 10:11 EDT||– Venus at inferior solar conjunction|
Over coming weeks, the distance between Venus and the Sun will decrease each night as it sinks back into the Sun's glare. The table below lists how long Venus will remain up after sunset each night; all times are given in Ashburn local time.
|Altitude of Venus
|Direction of Venus
|08 Aug 2018||20:10||22:04||20°||west|
|15 Aug 2018||20:01||21:50||20°||south-west|
|22 Aug 2018||19:52||21:35||18°||south-west|
|29 Aug 2018||19:42||21:19||17°||south-west|
|05 Sep 2018||19:31||21:01||15°||south-west|
|12 Sep 2018||19:20||20:43||13°||south-west|
|19 Sep 2018||19:09||20:22||11°||south-west|
|26 Sep 2018||18:57||19:58||9°||south-west|
|03 Oct 2018||18:46||19:31||6°||south-west|
|10 Oct 2018||18:35||19:00||3°||south-west|
|17 Oct 2018||18:25||18:27||0°||south-west|
A graph of the phase of Venus is available here.
The coordinates of Venus when it reaches dichotomy will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 15 August 2018|
4 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|03 Jun 2017, 01:58 EDT||– Venus at greatest elongation west|
|17 Aug 2018, 03:58 EDT||– Venus at greatest elongation east|
|06 Jan 2019, 01:02 EST||– Venus at greatest elongation west|
|24 Mar 2020, 03:31 EDT||– Venus at greatest elongation east|
© NASA/Ricardo Nunes